Hardness tester



P. 'CRAEMER mnmzssnsun and April 6. 1933 Sept. 11, 1934.

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Patented Sept. 11, 1934 UNITED sures PATENT OFFICE HARDNESS TESTER Paul Craemer, He'mbrock, Germany- Application April 6, 1933, Serial No. 664,826 7 In Germany March 30, 1932 1 Claim. (oi. ass-1s) The invention relates to a hardness tester which enables the hardness of work materials to .be directly read 0d quickly'and with suflicient accuracy'for any particular work in hand. The

new hardness tester is suitable, for example, as a control inst ument in conunerc'ial firms for iron, steel, sheet metal and the like, and in engineering work-shops, and is also particularly suitable'for pressing and stamping works which operate on waste sheet metal or various kinds which must he tested from time to time by a substantially accurate hardness test as to its suitability lor any work that may be required to be performed.

The new hardness testing device depends on the principle of the so-calledhall pressure system, i. c. it measures the impression produced in the work material by a pressure member under the test load, said impression varyinc accordina to the degree of hardness. in the measurement of hardness the test piece is always moved through the same path against the pressure member which has a limited longitumnal movement and which stands under the action or .a'load spring. so thatthe spring is practically always tensioned to the-same testing load. The impression thus produced by the pressure member in the work material-which impression varies accordinc to the hardness of the latter-is measured in a suitable manner and when converted into hardness values may be directly read ed on a scale with sumcient accuracy tor workinu reauirerooms. 3 i

Owinato the varying depth impressions oi the pressure member in the work material depending on the hardness of the letter, the sprinu I experiences a slight reliei oi tension so that the test load automatically set by the hearinp oi the test piece on the pressure memher is always somewhat smaller than the test load 'dueto a completely tensioned sprinc as would occur with infinitely hard work materials althouch these deviations from the theoretical maximum sprint,

A pressure are so small that they may he dimepardsuitable measuring tools in order to ohtaln the; with the aid or harness'value, as for ekclmple, the micrometer screw.

Aconstructional term of hardnem tested ecthe point or the pressure memher a is disposed in cording to the invention is illustrated in the accompanying drawing in which:

its. 1 is a front elevation,

his. l is a side elevation partly in section,

Fig. i is a plan view oi a reading disc.

The hardness tester illustratedin the drawing has a strong frame member 1 of general o -shape provided with a handle '2. An adjusting screw 3 rotatable by means 01a milled knob d is supported in one limb of the member 1. as The other end of the screw 3 extends into the space between the two limbs of the member 1 and carries a'test piece support 6 which rests on a hall 5 or thelike. A test piece P may be mounted on the support 6. to

A sleeve l is secured in the other limb of the member 1 co-arially with the screw 3. A reciprocatory rod 8 is supported within sleeve 7 and is provided at its and adjacent the screw 3 with a pressure memh r 9 comprising, for exis, ample, a hardened steel pin having a conical or spherical shaped end. The pressure member 9 is guided hy a sleeve it consisting, for example, of hardened steel theend races of which are accuratcly perpendicular to the common aris of so the parts 3 and t. The rod is placed under the action oi a loml spring ii, for example, a helical sprlnp which is placed in the sleeve '8 with a pre-' liminary tension and which bears at one end against a collar is on the rod t. The other end as, oi the sprint; hears aoainst an upper closure cap it which is screwed with a. tiuht ht on the sleeve 7 and which may he usedior accurately reaulatinc the tension or the sprine. The spring ll tends to move the rod s towards the screw 3, such movement'heinc limited by the collar is hearine on a shoulder termed in the interior of the sleeve "i. When, on the other hand, the rod is so liar moved towards the closure cap it that till the plane at the lower suriace oi the guide sleeve it, the sprints is strained to the maximum test load. 1

The upper eudoi the rod t is provided with a tine screw thread it on which is screwed a mo shove it provided with a pointer id. n can it is applied to the end cithe spindle so that the sleeve it can he screwed up and down hetween said cap and the upper surface oi the cap it is termed as a The, pointer idis provided with a sharp edse it and moves over a hardnoes indicator scale it (his. 3); v

in i We the newhardness' measur'er a test piece havlnu a decree oi hardnms'accuratetest piece is pushed between the pressure member 9 and the support 6 in order to compress the spring 11 and then the cap 12 is turned on the sleeve 7 and the sleeve 15 is screwed down on the screw thread 13 until the pointer edge 1'7 registers accurately with that division of the scale 18 on the upper surface of the cap disc 12 corresponding to the hardness of the work material measured in the laboratory. According as work materials subsequently measured with the instrument possess a greater or smaller hardness value so does the pointer edge move to the right or left of this division on the scale until it is temporarily prevented from further rotation in a position corresponding to the degree of hard-= ness of the material under test. Thus by employing standard test pieces of accurately determined or known hardness, and appropriately acl justing the pointer sleeve 15 with respect to the appropriately calibrated'hardness scale 18 hawing thereon indications of corresponding hardness values, the hardness of any desired material may be determined by pushing it between the pressure member 9 and support 6 and moving'it axially by means of the screw 3 until it bears against the lower face of sleeve 10, whereupon the sleeve 15 is turned towards the scale 18 until by binding on part 12, it is prevented from further rotation; in this position the pointer edge coincides with a definite division of the scale and thuswithout further difiiculty the ascertained degree of hardness can be read off numerically with anaccuracy completely sufficient for any working requirement.

After the reading has been taken and the ma terial under test has been removed, it is necessary for the sleeve 15 to be screwed back suf- 973,833 correctly adjusting the reading scale 18. This ficiently far towards the stop 16- to enable the tension of the spring to be slackened and to permit the return of the pressure member. With a' suitably selected pitch for the screw thread 13 sufiiciently large angular movements of the pointer edge over the scale corresponding to the differences of the impressions in the work under test are obtained without the employment of special means for magnifying the depths of the impressions to enable them to be measured and read. It is, of course, within the scope of the invention to provide other means than those hereinbefore described and illustrated in the drawing for enabling the variations in the com pression of the spring corresponding to the difierent degres of hardness to be directly read.

What I claim is:-

A hardness tester comprising a yoke-shaped frame, specimen-supporting means and a pence trating member and cooperating spindle disposed interiorly of the span of said yoke and movably mounted in the arms of said yoke, a sleeve disposed in that arm carrying the spindle, a closure cap having a scale thereon disposed around said spindle and threading on said sleeve, a permanently tensioned spring disposed about said spindle and abutting against the inner surface of said'closurevcap and tending to force the penetrating member inwardly, a cap disposed about the outer end of said spindle, and an indicator threaded on said spindle and disposed between said closure cap and said last-mentioned cap so as to be capable of limited rotation about said scale upon outward movement of said spindle against the tension of said spring to indicate the hardness of said test specimen.

PAUL CRAEMIER. 

